Lithium-based battery packs require battery management systems (BMS) to monitor important functions. These functions include the temperature, voltage, current, charging/discharging rates, capacity, and the overall health of the batteries. If an issue arises, such as high temperatures or overcharging, the BMS collects the data and sends it to the device's control system.
In turn, the control system will enact a specific command to address the issue. It may turn on cooling systems to vent the excess heat or cut off the charge state to the batteries.
Seamless communication between the BMS and the device is vital to ensure the health and safety of both the battery pack and the application. Battery communication protocols provide the connection between the BMS, the device, and the control system.
Types of Battery Communication Protocols
Companies may decide on proprietary battery communication protocols or standard protocols. Proprietary protocols are custom-designed for the battery pack and the device. This customization ensures reliability, while providing optimal performance since the design is catered to the application. Since proprietary communication protocols are application-specific, they normally cannot be used for other devices and are not interchangeable.
On the other hand, standard communication protocols are used by multiple manufacturers and customers. These protocols allow for greater levels of accessibility across multiple devices and components. They are for widespread use and provide good performance, yet not at a higher speed than communication protocols that are proprietary.
Battery communication protocols may involve a wired connection or a wireless connection based on distance, battery pack complexity, power consumption, data rate, the size of the network, and costs. If there are multiple connected systems requiring power and pack monitoring, a wired connection may be desired. For applications that can operate at lower data speeds and are mobile energy storage devices, wireless battery communication protocols can provide ideal benefits.
Communication Protocol Options
Battery communication protocols contain interface ICs to ensure seamless communication between the BMS and devices. The ICs provide a variety of functions depending on how the system is set up and data transfer rates.
Battery management system communication options.
- Controller Area Network (CAN): The CAN offers a multi-master setup that is decentralized. Data can be sent from a central bus from different nodes, as this offers reliability even if one of the nodes fails.
- RS 485: The RS 485 has a half-duplex transmission method where data transmission can occur in both directions yet does not occur at the same time. It offers long-distance communication between multiple battery packs that are distributed in a wide area, as it provides acceptable noise immunity from electromagnetic interference.
- Inter-Integrated Circuit (I2C): I2C is a synchronous serial method where communication occurs along a single bus over two wires. It offers low power consumption for brief intra-board communication at lower speeds.
- Universal Asynchronous Receiver-Transmitter (UART): The UART method has point-to-point communication where data is sent serially from one transmitter point to the next receiver point. It provides a simplified option for low-speed data transfer at short distances while using low power.
- Bluetooth Low Energy (BLE): BLE offers a wireless communication method for mobile and portable battery-operated devices. It can provide remote monitoring for shorter distances with energy-efficient operation.
Purpose of a Battery Communication Protocol
Battery communication protocols are sets of guidelines that electronic devices and BMS units follow on how to gather, control, and transmit data information between components. These protocols ensure that connected devices can interpret the data efficiently to provide a desired outcome. This outcome may vary depending on the application and the guidelines.
If there were no protocols, then the battery pack, BMS, and device may not properly communicate with each other regarding the state of the battery cells, charging phases, or discharging cycles. Transmission errors may occur or overload the device's receiver. In addition, users may not be aware that the data was never received by the control system.
Communication Format Guidelines
Communication format guidelines dictate how the data is formatted to ensure both the battery pack, BMS, and the device can interpret the information. This data is gathered as either packets or frames and transmitted to devices in the specified format. By following the specified format, there will not be any command delays by the control system when addressing problems with the battery pack.
Flow and Sequential Guidelines
The guidelines focus on how the data is managed by strict control over the amount of data that flows between the transmitter and receiver, so as not to overload systems. The data can be sent as packets, as these packets are put together into the appropriate sequence at the receiver's end.
Transmission Fault Detection Guidelines
Data transmission errors can occur, causing communication issues with duplicate commands or other issues. Battery communication protocols institute multiple guidelines to detect and correct transmission faults.
Addressing and Acknowledgment Guidelines
Addressing guidelines assign methods on how devices are addressed to receive and transmit data along the network. When the data is received, acknowledgment protocols can inform the sender that the data was received correctly.
Summary
While lithium-based batteries often rely on BMS for monitoring and will employ battery communication protocols, other battery chemistries, such as lead acid, nickel metal hydride (NMH), and nickel manganese cobalt (NMC), also use communication protocols.
When considering the costs and complexity of the battery communication protocol, it will be dependent on the amount of data transmitted, the speed of transmitted data, the number of devices and components connected to the battery pack and control system, and the distance between the battery pack and devices. It will also depend on whether you are relying on a wired or wireless connection. Typically, low-cost options provide lower speeds at shorter distances, while larger networks and proprietary custom systems will increase costs.
Key Takeaways
- Battery communication protocols ensure system safety and control: These protocols allow the battery management system (BMS) to communicate critical data, like temperature, charge state, and voltage, to the control system for proper response actions.
- Proprietary vs. standard protocols: Proprietary protocols are tailored for specific devices and ensure high performance but lack interchangeability, while standard protocols offer wider compatibility across multiple systems.
- Wired and wireless options depend on application needs: Wired connections like CAN, RS-485, I²C, and UART are preferred for complex systems and long distances, while wireless options like Bluetooth Low Energy (BLE) suit portable or low-power devices.
- Data management and transmission guidelines are essential: Protocols define how data packets are formatted, sequenced, addressed, and acknowledged to prevent overloads, errors, or communication failures.
- Selecting the right protocol depends on system complexity: Factors such as data rate, range, network size, and regulatory requirements determine whether a simple wired link or a more advanced wireless setup is the best fit.
